1. Field of the Invention
The present invention relates to an ultrasonic motor which drives a moving body by friction by making use of oscillations of an oscillating body which is excited by a piezoelectric element, and an electronic apparatus which mounts the ultrasonic motor thereon.
2. Background Art
An ultrasonic motor which uses a disc-shaped or an annular oscillating body is classified into a progressive wave type ultrasonic motor and a standing wave type ultrasonic motor depending on a type of oscillations generated in the oscillating body. The former requires two groups of electrodes for exciting two oscillations which differ from each other in phase in terms of position in the oscillating body. On the other hand, although the latter uses only one group of electrodes at the time of driving, the latter requires two groups of electrodes corresponding to two standing waves since it is necessary to displace a position of the standing waves which are excited in the oscillating body in changing the moving direction of a moving body.
In a state where each of these two groups of electrodes is constituted of a plurality of electrodes, when a method which connects conductive members such as lead lines to respective electrode is adopted, there exists a possibility that a manufacturing cost is pushed up, and oscillations of a oscillating body are interrupted so that the performance of the ultrasonic motor is lowered or large performance irregularities occur. To cope with such drawbacks, there has been known a technique in which two groups of electrodes are constituted such that, in one group of electrodes, every other divided electrode in the circumferential direction of a piezoelectric element is short-circuited at an inner peripheral side of the piezoelectric element and, in the other group of electrodes, remaining other divided electrodes are short-circuited at an outer peripheral side of the piezoelectric element.